It is common practice in residential construction to provide for example hot and cold water valves as well as a drain connection in the room where a washing machine is to be installed. Such valves and drain connections are frequently made through the use of a washing machine outlet box. During construction of the building, the washing machine outlet box is installed between the studs or other structural members. Valves are then mounted in the box, and connections to the hot and cold water supplies are made to the valves. In addition, the washing machine outlet box includes a connection for the drain. In this way all of the plumbing connections for a conventional washing machine are conveniently located and attractively mounted. Once the box has been installed, the drywall is installed and a trim panel covers the joint between the drywall and the outlet box.
In the past, valves to control the flow of hot and cold water have been made of brass or copper. In addition, valves have been made of plastics such as chlorinated polyvinyl chloride (CPVC). Plastic valves have the advantage over mental valves in that they are less expensive to manufacture and lighter to ship. These valves include an inlet conduit with external threads. To mount the valves to a mounting fixture such as in a washing machine outlet box, the inlet conduit is passed through a hole in the box and a nut is threaded onto the external threads of the inlet conduit and tightened down to securely clamp the valves to the box. Thereafter, an adaptor having the same thread cross section is screwed onto the inlet conduit and the plumbing pipes from the house are then connected to the adaptor.
If the house has plastic plumbing, the adaptor is also made of plastic. In this case the connection between the adaptor and the household plumbing is made through a solvent welding process, as is well known in the art. However, heretofore a mechanical, threaded connection was still necessary between the plastic valve and adaptor, which created a point of potential failure in the plumbing system and required installation effort on the part of the plumber to install the adaptor and to be sure the joint was water-tight.